Patricia Masinga, 36, had known she had HIV for about 10 years. She worked for an Aids organisation, so when, inevitably, she began to get sick, she was well placed to get treatment, and her youth and two children gave her every reason to fight to stay alive.

But even among educated, professional women such as Patricia, uncertainty and confusion about the safety of Aids drugs has started to take hold in South Africa. She opted for a diet of garlic and lemon instead. A month ago, she died.

Doctors and campaigners who have been struggling to increase the availability of Aids drugs to the 5 million HIV-infected people in South Africa are dismayed by the activities of a German-born doctor, Matthias Rath, who has reignited a life-and-death struggle in South Africa.

Dr Rath denounces Aids drugs and claims that all those who promote them are the paid lackeys of western drug companies. Vitamins, not drugs, are the cure for Aids - and cancer and diabetes too for that matter - he says, and there are those in the South African government who appear to give him credence.

He has appeared with the health minister, Manto Tshabalala-Msimang, who has made it clear she favours the healthy properties of garlic, lemon, beetroot and olive oil and will not back the use of the antiretrovirals which have stopped the death toll in the west.

Dr Rath's proclamations in full-page advertisements in the New York Times and International Herald Tribune, as well as the widely read Sowetan in South Africa, claim that Aids drugs are toxic and potentially deadly. Although the medical establishment denies his claims, the uncertainty they are creating has been deepened by the equivocal attitude of the government.

It has affected the Aids organisation that Patricia (not her real name) worked for, and some of the traditional healers, who now doubt the safety of the drugs. Patricia told a friend she was fearful of them. "A few weeks before she died a friend of hers asked me to try to get her proper medical help," said Mark Heywood, the treasurer of the Treatment Action Campaign and founder of the Aids Law Project. "But it was too late. We are hearing of a fear and uncertainty that is becoming a real obstacle."

The health minister declared last week she would not be pushed into putting people on treatment for HIV - there are 42,000 in the public sector on antiretroviral drugs at the moment, well below the hopes of the World Health Organisation which has set a global target of 3 million on treatment by the end of this year. Dr Tshabalala-Msimang has refused to condemn Dr Rath when invited to do so by journalists.

Dr Rath, who has offices in California, the Netherlands and, most recently, Cape Town, claims his vitamin supplements can prevent and cure most diseases.

He began his career working with Linus Pauling, the US scientist who won Nobel prizes for chemistry (1954) and peace (1962) before becoming most famous late in his long life for backing vitamin C as the cure for all ills.

Dr Rath has taken the advocacy of vitamins into all-out war on the pharmaceutical companies through the Dr Rath Health Foundation, funded by and supporting the internet sales which appear to have made him a lot of money. Rulings banning his strident publicity leaflets and website claims by the Advertising Standards Authority in the UK and the Food and Drug Administration in the US, together with detailed and damning critiques from the Swiss study group for complementary and alternative methods in cancer and the British Medical Journal, have not softened his messianic tone.

This week an influential group of Harvard scientists and the United Nations followed the South African Medical Association in publicly rejecting his claims about Aids. But whatever the establishment scientists say, Dr Rath is in danger of being believed by millions.

On his website, the full-page ads in the New York Times and International Herald Tribune appear as editorials. "Dr Rath speaks in the New York Times", one of them is headed, in the paper's typeface. "Call to the people and governments of the world. Stop Aids genocide by the drug cartel!"

The cartel, he says, includes not only George Bush, but Tony Blair and Gordon Brown, whose plan for Africa is said to be a ploy to increase the revenues of the British drug company GlaxoSmithKline. The antiretroviral drugs which scientists say have stopped the death toll in the west, damage the cells in the body which vitamins protect and repair, he claims.

Supporting him are some of the maverick US scientists whose argument that HIV was not the cause of Aids found favour with the South African president, Thabo Mbeki some years ago. They, too, said the drugs made people ill. David Rasnick, one of those scientists, has now joined Dr Rath in Cape Town. Both names appear in one of the New York Times adverts which details a "clinical pilot study" of 18 people with Aids in the Cape Town township of Khayelitsha who were said to improve after four weeks on the supplements.

According to the Treatment Action Campaign in South Africa, which has cajoled and fought with the government for access to treatment for some of the 5 million now infected with HIV there, Dr Rath's experiments with vitamins in Khayelitsha are probably illegal because he did not have approval to open clinics and offer any kind of therapy. Furthermore, the levels of vitamin C in the supplements were far beyond the 200mg a day recommended as safe by the US National Institutes of Health, says TAC, and could cause diarrhoea, which could kill somebody with Aids.

Dr Rath has in turn thrown a mountain of mud at TAC, accusing it of paying people to attend demonstrations calling for treatment and money-laundering funds from drug companies.

Yesterday TAC asked a Cape Town court for an injunction to prevent Dr Rath making such allegations, prior to a suit for defamation. "He's got a lot of money obviously and he uses it perniciously to spread false information about medical treatment not just for HIV," says Mr Heywood. "The problem is that in South Africa he has found fertile ground both because of the denialism that exists within our government with relation to the management and treatment of HIV but also because of Aids denialist groups, which he is pumping lots of money into."

The damage of the Rath publicity, say his many critics, is in undermining confidence in treatment which can, unlike vitamins, save lives. "It is very serious," says Nathan Geffen of TAC's head office. "People are dying because of confusion. Tens of thousands of South Africans are dying because they are too confused and scared of being stigmatised to find out about their HIV status and get treatment."

Ralf Langner, the international coordinator of the Rath foundation, denied that it hoped to make money selling vitamins in South Africa. Their mission, he said, was to inform people of the toxicity of the drugs and "support this government in its attempt to bring nutritional programmes forward".

Asked if people should stop taking antiretroviral drugs, he replied: "I think people should make an informed decision in being aware of the side effects that there are and should be aware of the natural possibilities to delay the onset of this disease." Critics such as the UN, he said, had been infiltrated by the pharmaceutical industry. He agreed that Dr Rath had a lot of opponents. "It's like it is when you are ahead of your time," he said.

Médecins sans Frontières, which runs three HIV clinics in Khayelitsha treating nearly 2,000 people with Aids drugs, said yesterday that after three years, four out of every five people on the treatment were still alive. Without drugs, half would have died within a year. Those who died mostly had advanced Aids before starting treatment. Only four deaths could be directly linked to drug toxicity.

MSF called on the ministry of health "to recognise the plight of people in advanced stages of HIV infection by unequivocally stating that nutrition alone will not save them from death. For them [drug] therapy remains the only hope for survival."